1. Field of the Invention
The present invention is directed to the use or aqueous polyisocyanate dispersions as binders for fiberglass.
2. Description of the Prior Art
It is known to produce fiberglass insulating materials by spraying glass or mineral wool felts with aqueous adhesives based on phenol/formaldehyde resins or urea-formaldehyde resins for the purposes of consolidation. The aqueous adhesives are applied to the glass directly below the spinner in which very hot liquid glass or mineral mass is converted into fibers. Accordingly, adhesives which have high water contents and do not contain volatile organic compounds are used to prevent fires. Low water contents (e.g.&lt;50%) usually do not allow even distribution of the polymer on the fibers. The water is evaporated during subsequent hardening of the adhesives and is removed with the exhaust gases.
Generally, it is not possible to prevent part of the adhesive components from decomposing and further contaminating the exhaust gases. This is an economic disadvantage because part of the adhesive is lost during formation of the bond. Above all, however, this process is attended by significant disadvantages when physiologically harmful, readily volatile components are given off with the exhaust gases, as in the case of formaldehyde-containing adhesives, for example. To avoid air pollution, scrubber systems have to be installed to absorb the volatile organic materials in water. This is not only a costly operation but also means that the resulting aqueous solutions of organic materials must be disposed of.
In response to this problem, it is disclosed in U.S. Pat. No. 4,190,459 to use combinations of waterglass and isocyanates as binders for mineral fiber mats. However, emulsions obtained from mixtures of polyisocyanates and waterglass are highly viscous. Therefore, they are more difficult to pump, spray and disperse into the air as binders for fiberglass when compared to lower viscosity emulsions. Also, in the hardening process, waterglass is converted into silica and soda and the soda can leach out when the mat is exposed to water. Accordingly, it would be desirable to further improve the system disclosed in U.S. Pat. No. 4,190,459.
Water dispersible polyisocyanates and methods for obtaining stable aqueous dispersions of hydrophobic polyisocyanates through chemical modification are known and disclosed in U.S. Pat. Nos. 4,176,118; 4,114,267; 4,142,030; 4,097,422: 4,052,347; 3,959,348: and 3,959,329. It is also disclosed in U.S. Pat. Nos. 4,105,594 and 4,129,696 to provide aqueous solutions or suspensions of hydrophobic polyisocyanates. Furthermore, it is known to use external surfactants or additives which are not reacted with polyisocyanates to achieve dispersibility of hydrophobic polyisocyanates in water as taught by British Patent 1,186,771. Finally, aqueous dispersions of hydrophobic polyisocyanates can also be generated in the absence of any surfactant or additives using mechanical devices which provide high sheer forces. However, the prior art does not suggest the use of these polyisocyanates as binders for fiberglass.
It is an object of the present invention to provide aqueous dispersions of polyisocyanates which are suitable as binders for fiberglass and which do not require the concurrent use of waterglass as disclosed in U.S. Pat. No. 4,190,459, while at the same time maintaining the desirable properties of these fiberglass binders without forming undesirable by-products. This objective may be achieved in accordance with the present invention. Surprisingly, it has been found that emulsions of polyisocyanates are effective binders for the consolidation of fiberglass for the production of fiberglass mats.